Method for determining and controlling the amount of finely divided particulate solids added to a stream of fluid

ABSTRACT

The amount of finely divided particulate solids added to a stream of fluid to form a mixture of the particulate solids and the fluid is determined by a method comprising (a) determining the temperature and quantity of fluid in a stream of fluid; (b) determining the temperature of the particulate solids; (c) determining the temperature of the mixture; and (d) calculating the amount of the particulate solids in the mixture. The method can also be used to control the amount of finely divided particulate solids added to the stream of a fluid. The fluid is at a different temperature than the finely divided solids.

This is a division of application Ser. No. 07/181,803, filed Apr. 15,1988 now U.S. Pat. No. 4,840,726, which was a continuation-in-part ofapplication Ser. No. 06/932,852, filed Nov. 20, 1986, now abandoned.

This invention relates to a method for determining the amount of finelydivided particulate solids added to a stream of a fluid.

This invention also relates to a method for controlling the amount offinely divided particulate solids added to a stream of fluid.

This invention also relates to a method for determining and controllingthe amount of particulate catalyst added to a fluid catalytic crackingprocess.

In many processes, it is necessary to transfer finely dividedparticulate solids from a storage vessel to a processing unit. Suchprocesses include a variety of chemical processes wherein particulatecatalyst is used. Such problems can also arise in other industries whereparticulate solids are produced or handled when it is necessary totransfer particulate solids from a first point to another point by theuse of a transfer line in which a flowing fluid is used to transport theparticulate solids through the line.

In such processes, it is frequently desirable that the amount ofparticulate solids transferred be accurately measured or closelycontrolled or both. In previous attempts to achieve such transportationand control, various devices such as conveyors and fluidized lines havebeen used. Such processes have frequently failed to achieve the desiredreliability and ease of handling and the desired control.

One instance in which it is highly desirable that finely dividedparticulate solids, i.e., particulate catalyst, be added to a process inan accurate and controlled manner, is the process generally referred toas "fluid catalytic cracking." Such a fluid catalyst cracking process isdescribed in the Chemical Engineers Handbook, John H. Perry, Editor,McGraw-Hill Book Company, 1950, Page 1619. Such processes are consideredto be known to those skilled in the art and are widely used in theprocessing of petroleum. It is desirable that the addition ofparticulate catalyst to such units be accomplished reliably anddesirably in a steady and controlled manner. In other words, slugs offresh catalyst can adversely effect the process efficiency and thefailure to add adequate amounts of particulate catalyst when desired canalso adversely effect the efficiency of the process. It is highlydesirable that fresh particulate catalyst be added at a steady ratesufficient to supply the desired make-up catalyst on a constant basis.

It has now been found that the amount of finely divided solids added toa stream of fluid to form a mixture of the particulate solids and thefluid can be determined by a method comprising (a) determining thetemperature and quantity of fluid in the stream of fluid; (b)determining the temperature of the particulate solids; (c) determiningthe temperature of the mixture; and (d) calculating the amount of theparticulate solids in the mixture. Such a method can also be used tocontrol the amount of finely divided particulate solids added to thestream of fluid. The fluid is at a different temperature than the finelydivided solids.

BRIEF DESCRIPTION OF THE DRAWING

The FIGURE is a schematic diagram of an embodiment of the process of thepresent invention.

DETAILED DECRIPTION OF THE DRAWING

The term "finely divided particulate solids" as used herein refers toparticulate solids of a size small enough so that the finely dividedparticulate solids can be entrained in a flowing stream of fluid. Suchfinely divided particulate solids are generally smaller than about 28Tyler mesh.

In the FIGURE, finely divided particulate solids are stored in a storagevessel 12 which includes a reduced diameter lower portion 12' whichfunctions to direct particulate solids from vessel 12 to a dischargeline 14 from vessel 12. Line 14 includes a valve 16 which regulates therate at which particulate solids are released from storage vessel 12.Particulate solids are released from storage vessel 12 as shown byarrows 34 via line 14 into a transfer line 18 to form a mixture ofparticulate solids and the fluid. Transfer line 18 is adapted to theflow of a fluid through transfer line 18 as shown by arrow 26 to moveparticulate solids from vessel 12 along transfer line 18 toward adesired point.

In the practice of the present invention, a temperature sensor 20including a sensing element 20' is positioned to determine thetemperature of particulate solids from storage vessel 12 dischargedthrough line 14 into line 18. As shown, sensor 20 determines thetemperature of particulate solids as they pass through discharge line14.

A temperature sensor 22 including a sensing element 22' is shown fordetermining the temperature of the fluid in transfer line 18 prior tomixture of the fluid with particulate solids from vessel 12. A secondtemperature sensor 24 including a sensing element 24' is shown fordetermining the temperature of the resulting mixture of fluid andparticulate solids downstream from the junction of transfer line 18 anddischarge line 14. A pressure sensor 28 including a sensing element 28'is shown in operative contact with transfer line 18 and a flow meter 30including a sensing element 30' is shown in operative contact withtransfer line 18. These lines and sensing elements are used to determinethe amount of fluid flowing in transfer line 18 and may comprise anysuitable sensing elements known to the art for such measurements. Asknown to those skilled in the art, a flow meter may be sufficient todetermine the amount of liquid flowing in transfer line 18 if liquid isused and similarly, the pressure and volume flowing in transfer line 18can be used to determine the amount of gas flowing in transfer line 18if gas is used as the fluid. The information determined from thesetemperature sensors and the measurement of the amount of fluid flowingthrough line 18 enables the calculation of the amount of particulatesolids added to transfer line 18 when the temperature of the particulatesolids added to transfer line 18 is different than the temperature ofthe fluid flowing through line 18. The heat capacities of the fluidflowing through line 18 and the particulate solids added to line 18 canbe determined by conventional means known to the art, obtained fromstandard references or the like. When the particulate solids comprisecatalyst, the heat capacity may be obtained from the catalyst supplier.

Desirably, the temperature difference between the fluid flowing throughline 18 and the particulate solids from vessel 12 is at least double thedifference between the temperature of the mixture flowing in line 18 asshown by arrow 26' after admixture of the particulate solids and theparticulate solids from vessel 12. Desirably, the temperature differencebetween the fluid in line 18 and the particulate solids is at least 50°F. and preferably is at least 100° F. It may be necessary to heat thefluid flowing through transfer line 18 prior to mixing, although theparticulate solids could be heated prior to mixing if desired.Preferably, the fluid is heated because of the greater ease in handlingand heating fluids.

Upon measurement of the temperatures referred to above, determination ofthe amount of fluid flowing through transfer line 18 and determinationof the heat capacities of the fluid flowing through line 18 and theparticulate solids added to line 18, the amount of particulate solidsadded to line 18 can be calculated as follows: ##EQU1## where: W_(c)equals the amount of particulate solids in the mixture in line 18,

W_(a) equals the amount of fluid flowing through line 18,

T_(a) equals the temperature of the fluid flowing through line 18 priorto (upstream from) the addition of particulate solids to line 18,

T_(c) equals the temperature of the particulate solids added to line 18,prior to the addition of the particulate solids to line 18,

T_(ac) equals the temperature of the mixture flowing in line 18,

C_(pa) equals the heat capacity of the fluid flowing through line 18,

C_(pc) equals the heat capacity of the catalyst added to line 18.

By the use of the formula set forth above, the amount of particulatesolids added to line 18 can be accurately determined. In the practice ofthe present method, the flow of fluid is initiated and particulatesolids are added at a selected rate. The temperature and amount of fluidand the amount of solids flowing through line 18 may be arbitrarilyselected initially. Upon calculating the amount of solids flowingthrough line 14 into line 18, the flow rate of the particulate solidscan be readily adjusted. By continuously or periodically checking theamount of solids flowing through line 18, the amount of solids added tothe process through line 18 can be readily controlled.

In the practice of the present invention, the fluid may be selected fromgases or liquids, depending upon the needs of the process user. Forinstance, if particulate solids are being transferred to a liquidprocess, it may be desirable to use a liquid as a transfer medium. Theliquid may be either oleaginous or aqueous, depending upon theparticulate solids transferred and the objectives of the user.

In other embodiments, it may be desirable to use a gas as a transferfluid. One such embodiment is fluid catalytic cracking processes asdiscussed previously. Such processes are known to those skilled in theart and in general comprise the reaction of petroleum fractions with aselected particulate catalyst in a reaction zone followed by recovery ofa spent catalyst stream from the reaction zone. The spent catalyststream is recycled to a regeneration zone where it is treated to producea regenerated catalyst, usually by burning carbonaceous materials fromthe catalyst, which is then returned to the reaction zone with freshhydrocarbon feed. It is possible to add fresh catalyst at a variety ofpoints in such processes. Desirably, the fresh catalyst is added by theuse of air as a transfer fluid with the resulting mixture of particulatecatalyst and air being injected into a transfer line to the regenerationzone or directly into the regeneration zone. In the event that it isdesired to add the fresh catalyst to the reaction zone, it is preferredthat an oleaginous liquid compatible with the reactions in the reactionzone be used as a transfer fluid for the catalyst. Such variations areclearly within the skill of those in the art and need not be discussedfurther.

As shown in the FIGURE, a controller 32 is in operative contact witheach of the sensors discussed previously to receive and processinformation to produce a determination of the amount of particulatesolids in line 18. This control may be accomplished manually bycalculation of the amount of catalyst or other particulate solids inline 18 or the control may be accomplished by periodic or substantiallycontinuous calculation of the amount of catalyst in line 18 by acomputer or the like. In either event, a line 34 is shown forcontrolling valve 16 in response to the determination of the amount ofcatalyst in line 18. Such accurate determination and control hashitherto been unavailable to the art. Previously, catalyst has beenadded to such processes by physically measuring the change in the heightof the particulate solids in vessel 12, by the use of small pots whichare manually filled with particulate solids and then discharged into atransfer line or the like. Such methods have been found to be inaccurateand cumbersome. Clearly, the use of the method of the present inventionrepresents a substantial improvement in methods for the addition ofparticulate solids to a process.

Having thus described the invention by reference to certain of itspreferred embodiments, it is pointed out that the embodiments discussedare illustrative rather than limiting in nature and many variations andmodifications are possible within the scope of the present invention.Many such variations and modifications may be considered obvious anddesirable by those skilled in the art upon a review of the foregoingdescription of preferred embodiments.

Having thus described the invention, I claim:
 1. A method fordetermining the amount of finely divided particulate solids added to astream of a fluid to form a mixture of said particulate solids and saidfluid, said fluid being at a different temperature than said particulatesolids, said method comprising:(a) determining the temperature andquantity of said fluid prior to addition of said particulate solids; (b)determining the temperature of said particulate solids prior to additionof said particulate solids to said fluid; (c) adding said particulatesolids to said stream of fluid to form a mixture of said particulatesolids and said fluid; (d) determining the temperature of said mixture;and (e) calculating the amount of said particulate solids in saidmixture according to the equation: ##EQU2## where: W_(c) equals theamount of particulate solids in said mixture,W_(a) equals the amount offluid in said stream of fluid, T_(a) equals the temperature of the fluidin said stream of fluid prior to addition of said particulate solids tosaid stream of fluid, T_(c) equals the temperature of the particulatesolids added to said stream of fluid prior to addition of saidparticulate solids to said stream of fluid, T_(ac) equals thetemperature of said mixture, C_(pa) equals the heat capacity of saidfluid, and C_(pc) equals the heat capacity of said particulate solids.2. The method of claim 1 wherein the difference between the temperatureof said fluid and the temperature of said particulate solids is at leastdouble the difference between the temperature of said mixture and thetemperature of said particulate solids.
 3. The method fo claim 1 whereinthe difference between the temperature of said fluid and the temperatureof said particulate solids is at least 50° F.
 4. The method of claim 3wherein said difference is at least about 100° F.
 5. The method of claim1 wherein said fluid is a gas.
 6. The method of claim 5 wherein said gasis air.
 7. The method of claim 1 wherein said particulate solids arecatalyst solids.
 8. The method of claim 1 wherein said fluid is aliquid.
 9. A method for dispersing controlled amounts of finely dividedparticulate solids from a finely divided particulate solids storagevessel through a transfer line, said transfer line being incommunication with a discharge line from said vessel to receive saidparticulate solids from said discharge line to produce a mixture of saidparticulate solids and a fluid in said transfer line said discharge lineincluding means for regulating the flow of said particulate solidsthrough said discharge line, said method comprising:(a) flowing saidfluid through said transfer line at a rate sufficient to move saidparticulate solids through said transfer line and at a temperaturedifferent than the temperature of said particulate solids; (b)determining the temperature of said particulate solids prior to additionof said solids to said fluid; (c) determining the temperature of saidfluid prior to addition of said solids to said fluid; (d) determiningthe amount of said fluid flowing in said transfer line; (e) discharginga quantity of said particulate solids into said transfer line at aselected discharge rate to produce said mixture; (f) determining thetemperature of said mixture; (g) calculating the amount of saidparticulate solids in said mixture by the equation: ##EQU3## where:W_(c) equals the amount of particulate solids in said mixture,W_(a)equals the amount of fluid flowing through said transfer line, T_(a)equals the temperature of the fluid flowing through said transfer lineprior to addition of said particulate solids to said transfer line,T_(c) equals the temperature of the particulate solids added to saidtransfer line prior to addition of said particulate solids to saidtransfer line, T_(ac) equals the temperature of the mixture flowing insaid transfer line, C_(pa) equals the heat capacity of the fluid flowingthrough said transfer line, C_(pc) equals the heat capacity of theparticulate solids added to said transfer line, and (h) controlling saiddischarge rate of said solids to a desired rate based upon saidcalculation.
 10. The method of claim 9 wherein the difference betweenthe temperature of said fluid and the temperature of said particulatesolids is at least double the difference between the temperature of saidmixture and the temperature of said particulate solids.
 11. The methodof claim 9 wherein the difference between the temperature of said fluidand the temperature of said particulate solids is at least 50° F. 12.The method of claim 11 wherein said difference is at least about 100° F.13. The method of claim 9 wherein said fluid is a gas.
 14. The method ofclaim 13 wherein said gas is air.
 15. The method of claim 9 wherein saidparticulate solids are catalyst solids.
 16. The method of claim 9wherein said fluid is a liquid.
 17. The method of claim 9 wherein saidparticulate solids comprise fluid catalyst cracking process catalyst.